Pulley set for a continuously variable transmission unit

ABSTRACT

A pulley set for a continuously variable transmission unit, comprises a pair of discs accommodated on a shaft, and a screw mechanism which is concentric with respect to said discs and for moving the discs towards and from each other, said discs enclosing a V-shaped groove, for accommodating a belt, said screw mechanism being controllable by a control means. The control means including a motor unit, said motor unit comprising a stator and a rotor, one of said stator and rotor engaging the nut of the screw mechanism, and the other of said stator and rotor engaging the screw of the screw mechanism.

BACKGROUND OF THE INVENTION

1. Field of Invention

The invention is related to a pulley set for a continuously variabletransmission unit, comprising a pair of discs accommodated on a shaft,and a screw mechanism which is concentric with respect to said discs andfor moving the discs towards and from each other, said discs enclosing aV-shaped groove, for accommodating a belt, said screw mechanism beingcontrollable by a controller, wherein said controller includes a motorunit, said motor unit including a stator and a rotor, one of said statorand rotor engaging the nut of the screw mechanism, and the other of saidstator and rotor engaging the screw of the screw mechanism, thecontroller having two linked satellite gear wheel systems, one of whichconnects the rotor or the stator to the nut, and the other of whichconnects the other of said rotor or the stator to the nut, and the otherof which connects the other of said rotor or stator to the screw, saidsatellite gear wheel systems each comprising a ring gear wheel, a sungear wheel and satellite gear wheels.

2. Description of Related Art

A continuously variable transmission having such pulley sets is knownfrom EP A 582307. The screw mechanisms of the pulley sets are controlledby a common, single motor, which is offset with respect to said screwmechanisms. The motor engages the screw mechanism through a number ofintermediate gear wheels and auxiliary shafts.

As a result, this prior art continuously variable transmission unit iscomplicated, and therefore prone to malfunction. Moreover, its overalldimensions are rather large.

SUMMARY OF THE INVENTION

The object of the invention is to provide a pulley set for acontinuously variable transmission, which does not have thesedisadvantages. This object is achieved in that the sun gear wheels orthe ring gear wheels are fixedly connected together.

The pulley set according to the invention may have its own motor unit.This allows a rapid and independent control of the gap of the pulleyset. As a result, the pinching force exerted by the discs on the beltcan be regulated as required, in particular in order to avoid slip.Also, a rapid transmission ratio change is made possible.

In case the screw mechanism is static in relation to the nut, the screwmechanism and the nut have the same rotational speed. The transmissionratio is then constant, and the motor keeps the screw mechanism, andthus the discs of the pulley set, in a static position. That is, thediscs enclose a gap which remains of constant width.

Upon a relative rotation between the rotor and the stator of each motor,a change in said gap is generated due to the action of the screwmechanism.

The required reduction between the motor and screw mechanism ispreferably obtained by means of at least one satellite gear wheelsystem. For instance, each controller may comprise two linked satellitegear wheel systems, one of which connects the rotor or the stator to thenut, and the other of which connects the other of said rotor or statorthe screw, said satellite gear wheel systems each including a ring gearwheel, a sun gear wheel and satellite gear wheels.

The pulley set having two linked satellite gear wheel systems may becarried out in several ways.

According to a first embodiment, the ring gear wheels are connected tothe stator respectively to the rotor, and the sun gear wheels areconnected to each other.

According to a second embodiment, the sun gear wheels are connected tothe stator respectively to the rotor, and the ring gear wheels areconnected to each other.

According to a third embodiment, the satellite gear wheels of eachsatellite gear wheel system are accommodated on a respective carrier,said carriers being connected to the stator respectively to the rotor,and the sun gear wheels are connected to each other.

According to the fourth embodiment, the satellite gear wheels of eachsatellite gear wheel system are accommodated on a carrier, said carrierbeing connected to the stator respectively to the rotor, and the ringgear wheels are connected to each other.

The gear ratios of the satellite gear wheel systems should be identical.

Preferably, the satellite gear wheel systems are coaxial and havecoaxial ring gear wheels and coaxial sun gear wheels.

The diameters of the ring gear wheels can be identical. Also, thediameters of the sun gear wheels can be identical, and the diameters ofthe satellite gear wheels can be identical.

The sun gear wheel of a satellite gear wheel system may be connected tothe shaft, and the ring gear wheel of a satellite gear wheel system maybe connected to the shaft. Also, the carriers for the satellite gearwheels may be connected to the shaft.

Preferably, an electric motor is applied in the controller, which may beconcentric with relation to the pulley set.

The invention also relates to a continuously variable transmissionincluding two pulley sets as described before and an endless beltstretching between said sets and accommodated in the grooves thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1-4 shows embodiments of the pulley set according to theinvention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The invention will be explained further with reference to the embodimentof the pulley sets shown in the figures.

The pulley set in FIG. 1 comprises two discs 1, 2, mounted on a shaft 3.In the embodiment shown, disc 1 is fixedly connected to shaft 3, whereasdisc 2 is slidably, but non-rotatably through groove/ball connection 4,accommodated on the shaft 3.

The discs 1, 2 enclose a V-shaped groove 5, the width of which can bevaried upon shifting the slidable disc 2. The V-shaped groove 5accommodates a belt 50, such as an endless belt, a flexible toothedbelt, a chain drive, a direct gear transmission, pull belt or push belt.

To that end, the discs 1, 2 are connected to a screw mechanism 6, theaction of which is controllable by means of controller 7. In particular,the screw 8 of the screw mechanism 6 is connected to slidable disc 2 bymeans of a yoke 9. This yoke 9 has legs 10 which protrude through holes11 which are arranged in the wall 12 of screw mechanism housing 13 whichaccommodates the screw mechanism 6.

The screw mechanism housing 13 is connected to the support shaft 3 andthereby to the fixed disc 1. Within the screw mechanism housing 13, thenut 14 of the screw mechanism 6 is rotatably fixed in axial direction,supported by means of bearing 15. The nut 14 and the screw 8 engage eachother through grooved rollers 16. Alternatively, balls may be appliedinstead of grooved rollers.

According to the invention, the nut 14 is accommodated in a sleeve 17,which is connected through a carrier 40 and shaft 41 to the firstsatellite gear wheels 20.

These satellite gear wheels 20 form part of a first satellite gear wheelsystem 19, which further include a first sun wheel 18, a ring gear wheel21, and a number of satellite gear wheels 20 mounted rotatably on thecarrier 40. In turn, the ring gear wheel 21 is connected to the rotor ofelectric motor 23, which electric motor 23 furthermore comprises astator 24.

The screw mechanism housing 13 is connected to the second satellite gearwheels 27, which form part of a second satellite gear wheel system 26.This second gear wheel system 26 further includes a second sun gearwheel 25, as well as a second ring gear wheel 28. This second ring gearwheel 28 is connected to the first ring gear wheel 21.

The screw mechanism housing 13 is rotatably supported with respect tothe stator housing 29 by a bearing 31. Furthermore, the ring gear wheel21 is rotatably supported with respect to the stator housing 29 througha bearing 32.

In service of the pulley set in a continuously variable transmissionunit, and in the case of a constant width of the V-shaped groove 5, thescrew mechanism housing 13 rotates at the same rotational speed as theshaft 3, the motor housing 29 is stationary. The motor 23 acts to as tokeep the nut 14 and the screw 8 in a fixed relative position, by makingthe rotor 22 stand still.

Upon changing the width of the groove 5 however, the motor 23 isactivated in such a way that the rotor 22 is rotated with respect to thestator 24. As a result, the satellite gear wheels 20, 27 make the sungear wheel 18 rotate with respect to the sun gear wheel 25, whereby thenut 14 is rotated with respect to the screw. The screw mechanism 13 thusmakes the disc 2 move towards or from fixed disc 1.

The embodiment of FIG. 2 to some extent corresponds to the embodiment ofFIG. 3. However, the rotor 22 now is connected to the sun wheel 18 ofthe first satellite gear wheel system 33. The ring gear wheel 21 and thesun gear wheel 18 engage each other by means of the first satellite gearwheels 20.

The ring gear wheel 21 of this first system 33 is connected to thesecond ring gear wheel 28 of the second satellite gear wheel system 26.The sun gear wheel 18 of the first satellite gear wheel system 33 issupported with respect to the axle stub shaft by means of bearing 37.The second sun gear wheel 25 of the second satellite gear wheel system26 is connected to the motor housing 29 through an axle stub 34. The sungear wheel 25 and the ring gear wheel 28 of the second system 26 engageeach other through the second satellite gear wheels 27. Screw mechanismhousing 13 is rotatably supported with respect to stator housing 29, bybearing 31.

In the embodiment of FIG. 3 the carrier 40 of the satellite gear wheels20 of the first satellite gear wheel system 19 is connected to the rotor22 of the motor 23. The carrier 42 of the satellite gear wheels 27through shaft 43 is connected to the stator 22 of said motor 23.

The sun gear wheels 18, 25 are interconnected, whereas ring gear wheel21 engages the screw 8 through the screw mechanism housing 13 and theyoke 9, and ring gear wheel 28 engages the nut 14 with sleeve 17.

In the embodiment of FIG. 4, the outer rings 21, 28 are interconnected.The carrier 40, 42 are connected to the rotor 24 respectively to thestator 22. The sun gear wheels 18, 25 are connected to the nut 14 withsleeve 17, respectively to the screw 18 through the screw mechanismhousing 13 and the yoke 9.

Although in the embodiments shown one of the pulley discs is fixed andone pully disc is slidable with relation to the shaft, the invention isalso related to pulley sets wherein both polley discs are slidable withrelation to the shaft (symmetrical movement).

What is claimed is:
 1. Pulley set for a continuously variabletransmission unit, comprising: a pair of discs accommodated on a shaft,and a screw mechanism which is concentric with respect to said discs andfor moving the discs towards and from each other, said discs enclosing aV-shaped groove, for accommodating a belt, said screw mechanism beingcontrollable by a control means, wherein said control means includes amotor unit including a stator and a rotor, one of said stator and rotorconnected to a nut of the screw mechanism, and the other of said statorand rotor connected to the screw of the screw mechanism, the controlmeans comprising two linked satellite gear wheel systems, one of whichconnects the rotor or the stator to the nut, and the other of whichconnects the other of said rotor or stator to the screw, said satellitegear wheel systems each comprising a ring gear wheel, a sun gear wheeland satellite gear wheels, characterised in that the sun gear wheels orthe ring gear wheels are fixedly connected together.
 2. Pulley setaccording to claim 1, wherein the satellite gear wheels of eachsatellite gear wheel system are accommodated on a respective carrier,said carriers being connected to the rotor and stator respectively andthe sun gear wheels are connected to each other.
 3. Pulley set accordingto claim 1, wherein the satellite gear wheels of each satellite gearwheel system are accommodated on a carrier, said carriers beingconnected to the rotor respectively to the stator, and the ring gearwheels are connected to each other.
 4. Pulley set according to claim 1,wherein the gear ratios of the satellite gear wheel systems areidentical.
 5. Pulley set according to claim 1, wherein the satellitegear wheel systems are coaxial and have coaxial ring gear wheels andcoaxial sun gearwheels.
 6. Pulley set according to claim 1, wherein bothsatellite gear wheel systems are driveable by a common motor.
 7. Pulleyset according to claim 1, wherein each satellite gear wheel system isdriveable by means of a coaxial motor.
 8. Pulley set according to claim1, wherein the diameters of the ring gear wheels are identical. 9.Pulley set according to claim 1, wherein the diameters of the sun gearwheels are identical.
 10. Pulley set according to claim 1, wherein thediameters of the satellite gear wheels are identical.
 11. Pulley setaccording to claim 1, wherein the sun gear wheel of a satellite gearwheel system is connected to the shaft.
 12. Pulley set according toclaim 1, wherein the ring gear wheel of a satellite gear wheel system isconnected to the shaft.
 13. Pulley set according to claim 1, wherein thesatellite gear wheels of a satellite gear wheel system are connected tothe shaft.
 14. Pulley set according to claim 1, wherein one of the discsis fixed on the shaft, and the other disc is slidable with respect tothe shaft and fixed to the screw.
 15. Pulley set according to claim 1,wherein the motor is an electric motor.
 16. Continuously variabletransmission, comprising: at least one pulley set, one of which being apulley set according to claim 1, and an endless belt stretching betweensaid sets and accommodated in the grooves thereof.
 17. Continuouslyvariable transmission according to claim 16, wherein the at least onepulley set is connected to a single motor unit.
 18. Pulley set accordingto any of claims 4-17, wherein the sun gear wheel (25) of a satellitegear wheel system (26) is connected to the shaft (3).
 19. Continuouslyvariable transmission according to claim 16, wherein the endless belt isa pull belt.
 20. Continuously variable transmission according to claim16, wherein the endless belt is a push belt.